Articles de revues : « Nanocrystals Synthesis »

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Mohammadrezaee, Mohammad, Naser Hatefi-Kargan et Ahmadreza Daraei. « Enhancing crystal quality and optical properties of GaN nanocrystals by tuning pH of the synthesis solution ». Zeitschrift für Naturforschung A 75, n^o 6 (26 mai 2020) : 551–56. http://dx.doi.org/10.1515/zna-2019-0378.

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AbstractGallium nitride nanocrystals as a wide bandgap semiconductor material for optoelectronic applications can be synthesized using chemical methods. In this research using co-precipitation and nitridation processes gallium nitride nanocrystals have been synthesized, and by tuning pH of the synthesis solution at the co-precipitation step, crystal quality and optical property of the resultant gallium nitride nanocrystals have been enhanced. Gallium nitride nanocrystal samples were synthesized using solutions with pH values of 2.1, 4.8, 7.8, and 9.0, and then nitridation at 950 °C under the flow of ammonia gas. The synthesized nanocrystal samples were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and photoluminescence techniques. The XRD data show that the nanocrystals have hexagonal wurtzite crystal structure, and using Scherer’s equation the sizes of the synthesized nanocrystals are 23.6, 26.6, 19.7, and 10.4 nm for the samples synthesized using the solutions with pH values of 2.1, 4.8, 7.8, and 9.0 respectively. The sizes of the nanocrystals obtained from SEM images are larger than the values obtained using Scherer’s equation, due to the aggregation of nanocrystals. EDX spectra show that pH of the synthesis solution affects the elemental stoichiometry of the gallium nitride nanocrystals. We obtained better stoichiometry for the nanocrystal sample synthesized using solution with the pH of 4.8. Photoluminescence spectra show that for this sample the emission intensity is higher than the others.

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Lin, Weyde M. M., Maksym Yarema, Mengxia Liu, Edward Sargent et Vanessa Wood. « Nanocrystal Quantum Dot Devices : How the Lead Sulfide (PbS) System Teaches Us the Importance of Surfaces ». CHIMIA International Journal for Chemistry 75, n^o 5 (28 mai 2021) : 398–413. http://dx.doi.org/10.2533/chimia.2021.398.

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Semiconducting thin films made from nanocrystals hold potential as composite hybrid materials with new functionalities. With nanocrystal syntheses, composition can be controlled at the sub-nanometer level, and, by tuning size, shape, and surface termination of the nanocrystals as well as their packing, it is possible to select the electronic, phononic, and photonic properties of the resulting thin films. While the ability to tune the properties of a semiconductor from the atomistic- to macro-scale using solution-based techniques presents unique opportunities, it also introduces challenges for process control and reproducibility. In this review, we use the example of well-studied lead sulfide (PbS) nanocrystals and describe the key advances in nanocrystal synthesis and thin-film fabrication that have enabled improvement in performance of photovoltaic devices. While research moves forward with novel nanocrystal materials, it is important to consider what decades of work on PbS nanocrystals has taught us and how we can apply these learnings to realize the full potential of nanocrystal solids as highly flexible materials systems for functional semiconductor thin-film devices. One key lesson is the importance of controlling and manipulating surfaces.

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Komarov, Fadey, Altynay Togambayeva, Ludmila Vlasukova, Irina Parkhomenko, Oleg Milchanin, Maksim Makhavikov et Murat Tolkynay. « Ion-Beam Synthesis of InSb Nanocrystals in Si Matrix ». Advanced Materials Research 679 (avril 2013) : 9–13. http://dx.doi.org/10.4028/www.scientific.net/amr.679.9.

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The results of structural and optical investigation of crystalline Si with embedded InSb nanocrystals are reported. These nanocrystals were synthesized in silicon matrix by means of high-fluence “hot” implantation of Sb and In ions followed by thermal treatment. TEM gives an evidence of nanocrystal formation in implanted and annealed samples as well as an existence of microtwins and dislocation-type defects and substantial residual mechanical strains. We have identified nanocrystals as InSb from RS data. Mechanical strains in “silicon – InSb nanocrystals” system have been evaluated, too.

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Svrcek, Vladimir. « (Invited) Atmospheric Plasmas Synthesized Nanocrystals with Quantum Confinement and Quantum Hybrids in Photovoltaics ». ECS Meeting Abstracts MA2022-02, n^o 19 (9 octobre 2022) : 889. http://dx.doi.org/10.1149/ma2022-0219889mtgabs.

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Nanocrystals share lot of advantages of organics namely scalable and controlled synthesis, an ability to be processed in solution while additionally retaining the broadband absorption and superior transport properties of traditional photovoltaic semiconductors. Nanocrystal solar cells have the potential to considerably increase the maximum attainable thermodynamic conversion efficiency (> 50%). Nanocrystal solution-processed can be used in solar cell structure not only as an absorber but also as electron and hole transport layer where the HOMO and LUMO levels can be efficiently controlled by size and/or plasma induced surface engineering directly in colloidal solution. Solution-processed and surface engineered nanocrystals with quantum confinement can be then further used to fabricate new class of quantum hybrids when blended for instance with polymers or perovskites and serves as absorbing and/or e-h transporting material. In this presentation, we overview the atmospheric plasma-based approaches to synthesis and surface engineering of nanocrystals with quantum confinement. We will compare surface engineering by fs laser processing in liquid solutions and synthesis of nanocrystals with strong quantum confinement by atmospheric plasmas. Moreover, to understand the thermal stability of nanocrystals observed experimentally, we calculate the cohesive and the formation energies of nanocrystals by means of first-principle calculations. Finally, we overview our recent progress in integration of surface engineered nanocrystal as a quantum hybrids incorporated within perovskites solar cells.

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Kim, Jong Ung, Jeong A. Lee, Beyong Hwan Ryu, Ki Won Jun, In Ho Kim et Young Min Choi. « Synthesis and Characterization of PbSe Nanocrystals by a Microchannel Reactor ». Solid State Phenomena 124-126 (juin 2007) : 1285–88. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.1285.

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The synthesis of high-quality monodispersed nanocrystal is very important. Typical synthetic method is rapid nucleation by injection of an organometallic precursor into a solvent maintaining the reaction temperature. Since these methods are discontinuous processes, they are not efficient for large-scale production of monodisperse nanocrystals. In this study, continuous microchannel reaction technique is presented for synthesis of monodisperse lead selenide nanocrystals in a diphenyl ether as high-temperature organic media. The microchannel reactor was used due to its possibility of continuous process and reproducibility of narrow size distribution in nanocrystal synthesis. The synthesis was carried out in microchannel reactor (800 μm diameter) made from PTFE. Lead oleate and TOP-Se were used as organic precursor and diphenyl ether as high-temperature organic solvents. Lead selenide particles with a size of less than 10nm could be continuously prepared by this method. The nanocrystals have been characterized by X-ray diffraction, TEM and optical absorption spectrometer.

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Feng, Anni, Jiankang Cao, Junying Wei, Feng Chang, Yang Yang et Zongyuan Xiao. « Facile Synthesis of Silver Nanoparticles with High Antibacterial Activity ». Materials 11, n^o 12 (8 décembre 2018) : 2498. http://dx.doi.org/10.3390/ma11122498.

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We report on a reverse microemulsion method for the synthesis of silver nanocrystals and examine their antibacterial activities. As the molar ratio of water to sodium bis(2-ethylhexyl) sulfosuccinate (AOT) increases to 25, a morphology transition from a sphere-like nanocrystal to a wire-like one was observed. For both the gram-negative and gram-positive bacteria, the wire-like silver nanocrystal showed higher antibacterial activities. We conclude that the morphology of silver nanocrystals dominates their antibacterial activity.

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Xiong, Zichang, Himashi P. Andaraarachchi, Jacob T. Held, Rick W. Dorn, Yong-Jin Jeong, Aaron Rossini et Uwe R. Kortshagen. « Inductively Coupled Nonthermal Plasma Synthesis of Size-Controlled γ-Al2O3 Nanocrystals ». Nanomaterials 13, n^o 10 (12 mai 2023) : 1627. http://dx.doi.org/10.3390/nano13101627.

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Gamma alumina (γ-Al2O3) is widely used as a catalyst and catalytic support due to its high specific surface area and porosity. However, synthesis of γ-Al2O3 nanocrystals is often a complicated process requiring high temperatures or additional post-synthetic steps. Here, we report a single-step synthesis of size-controlled and monodisperse, facetted γ-Al2O3 nanocrystals in an inductively coupled nonthermal plasma reactor using trimethylaluminum and oxygen as precursors. Under optimized conditions, we observed phase-pure, cuboctahedral γ-Al2O3 nanocrystals with defined surface facets. Nuclear magnetic resonance studies revealed that nanocrystal surfaces are populated with AlO6, AlO5 and AlO4 units with clusters of hydroxyl groups. Nanocrystal size tuning was achieved by varying the total reactor pressure yielding particles as small as 3.5 nm, below the predicted thermodynamic stability limit for γ-Al2O3.

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Chernomordik, B. D., A. E. Béland, N. D. Trejo, A. A. Gunawan, D. D. Deng, K. A. Mkhoyan et E. S. Aydil. « Rapid facile synthesis of Cu2ZnSnS4 nanocrystals ». J. Mater. Chem. A 2, n^o 27 (2014) : 10389–95. http://dx.doi.org/10.1039/c4ta01658k.

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A method for rapid synthesis of 2–40 nm diameter nanocrystal dispersions of the emerging sustainable thin-film solar absorber copper zinc tin sulfide is reported: the average crystals size is controlled by varying the synthesis temperature between 150 °C and 340 °C. Films cast from larger nanocrystals, are crack-free and suitable for making thin film solar cells.

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Gao, Yukun, et PG Yin. « Synthesis of cubic CdSe nanocrystals and their spectral properties ». Nanomaterials and Nanotechnology 7 (1 janvier 2017) : 184798041770174. http://dx.doi.org/10.1177/1847980417701747.

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The cadmium selenide nanocrystals are prepared by colloidal chemistry under mild conditions. X-ray diffraction and high-resolution transmission electron microscopy measurements indicate that as-prepared cadmium selenide nanocrystals are zinc blende cubic structure. We carry out an analysis of quantum size effect in the Raman spectra of cadmium selenide nanocrystals performed by utilizing the chemical bond theory of Raman peak shift developed recently. It is revealed that the shifts of Raman peaks in cadmium selenide nanocrystals result from the overlapping of the quantum effect shifts and surface effect shifts. The sizes of the as-prepared cadmium selenide nanocrystals obtained by employing the Raman peak shift theory are in good agreement with the nanocrystal sizes determined by high-resolution transmission electron microscopy.

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Della Gaspera, Enrico, Noel W. Duffy, Joel van Embden, Lynne Waddington, Laure Bourgeois, Jacek J. Jasieniak et Anthony S. R. Chesman. « Plasmonic Ge-doped ZnO nanocrystals ». Chemical Communications 51, n^o 62 (2015) : 12369–72. http://dx.doi.org/10.1039/c5cc02429c.

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Di Tocco, Aylén, Gabriela Valeria Porcal, Walter Iván Riberi, María Alicia Zon, Héctor Fernández, Sebastian Noel Robledo et Fernando Javier Arévalo. « Synthesis of stable CdS nanocrystals using experimental design : optimization of the emission ». New Journal of Chemistry 43, n^o 32 (2019) : 12836–45. http://dx.doi.org/10.1039/c9nj02145k.

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Yang, Tung-Han, Shan Zhou, Kyle D. Gilroy, Legna Figueroa-Cosme, Yi-Hsien Lee, Jenn-Ming Wu et Younan Xia. « Autocatalytic surface reduction and its role in controlling seed-mediated growth of colloidal metal nanocrystals ». Proceedings of the National Academy of Sciences 114, n^o 52 (11 décembre 2017) : 13619–24. http://dx.doi.org/10.1073/pnas.1713907114.

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The growth of colloidal metal nanocrystals typically involves an autocatalytic process, in which the salt precursor adsorbs onto the surface of a growing nanocrystal, followed by chemical reduction to atoms for their incorporation into the nanocrystal. Despite its universal role in the synthesis of colloidal nanocrystals, it is still poorly understood and controlled in terms of kinetics. Through the use of well-defined nanocrystals as seeds, including those with different types of facets, sizes, and internal twin structure, here we quantitatively analyze the kinetics of autocatalytic surface reduction in an effort to control the evolution of nanocrystals into predictable shapes. Our kinetic measurements demonstrate that the activation energy barrier to autocatalytic surface reduction is highly dependent on both the type of facet and the presence of twin boundary, corresponding to distinctive growth patterns and products. Interestingly, the autocatalytic process is effective not only in eliminating homogeneous nucleation but also in activating and sustaining the growth of octahedral nanocrystals. This work represents a major step forward toward achieving a quantitative understanding and control of the autocatalytic process involved in the synthesis of colloidal metal nanocrystals.

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Mukai, Kohki, et Kevin Nakayama. « Study on chemical synthesis of SnSSe nanosheets and nanocrystals ». Japanese Journal of Applied Physics 61, SC (9 février 2022) : SC1012. http://dx.doi.org/10.35848/1347-4065/ac3d0d.

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Abstract Two kinds of raw material combinations for the hot injection method were investigated for the chemical synthesis of SnSSe nanosheets and nanocrystals, which are low-toxic optoelectronic materials. When SnSe quantum dots were synthesized by mainly using oleic acid as the Se precursor solvent, the quantum dots changed from spherical to cubic as the size increased. The growth condition dependence of the nanocrystal formation process was discussed. When SnSSe nanocrystals were synthesized by mainly using trioctylphosphine as the S Se precursor solvent, it was found that the nanocrystal shape changed from dot to rod or sheet by reducing the proportion of S. The bandgap energy did not simply depend on the composition ratio of S but was affected by the change in the nanocrystal shape depending on the quantum confinement effect.

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Méndez-López, A., A. Morales-Acevedo, Y. J. Acosta-Silva et M. Ortega-López. « Synthesis and Characterization of Colloidal CZTS Nanocrystals by a Hot-Injection Method ». Journal of Nanomaterials 2016 (2016) : 1–7. http://dx.doi.org/10.1155/2016/7486094.

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The present study reports the synthesis of colloidal Cu2ZnSnS4(CZTS) nanocrystals (average size ~4–9 nm) by a simple and low cost hot-injection method. These nanocrystals form larger particles with sizes around 40 nm. Oleylamine (OLA) was used as both the solvent and the nanocrystal stabilizer. The effect of the synthesis time on the structural, compositional, morphological, and optical properties was studied. As revealed by XRD, Raman, and TEM measurements all the prepared samples are comprised of both kesterite and wurtzite CZTS nanocrystals. The wurtzite phase contribution reduces as the reaction time is increased. The “bandgap” of the obtained nanoparticles tends to 1.52 eV for the larger synthesis times (24 h) which is suitable for an absorber layer in thin films solar cells.

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Murray, C. B., Shouheng Sun, W. Gaschler, H. Doyle, T. A. Betley et C. R. Kagan. « Colloidal synthesis of nanocrystals and nanocrystal superlattices ». IBM Journal of Research and Development 45, n^o 1 (janvier 2001) : 47–56. http://dx.doi.org/10.1147/rd.451.0047.

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Erdogan, A., C. Karakaya, M. K. Gonce, S. Buyukcelebi, E. Yenel, K. Kara, A. N. Ozcivan, M. Can, M. Kus et S. Demic. « Surface modification of CdSeS nanocrystals for polymer hybrid solar cells ». RSC Advances 6, n^o 33 (2016) : 27627–31. http://dx.doi.org/10.1039/c5ra27735c.

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Chen, Kuan-Ting, Wei-Chung Chang, Shu-Chen Lu, Po-Yuan Yang et Hsing-Yu Tuan. « Facile Synthesis of Cu Nanocrystals with Morphology Evolution from Transitional Truncated Octahedra to Octahedra ». Journal of Nanomaterials 2019 (26 décembre 2019) : 1–7. http://dx.doi.org/10.1155/2019/2890162.

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Growth of Cu polyhedral structures with well-defined and controllable shapes faced tremendous synthetic challenges in colloid nanocrystal synthesis in the past few decades. In this article, we report a facile approach for the synthesis of Cu nanocrystals with systematic morphological evolution. Transitional truncated octahedral, edge- and corner-truncated octahedral, all-corner-truncated octahedral, and octahedral structures were obtained in a solution-based reduction reaction by precise tuning reaction time. Four distinct morphologies of nanocrystals have been characterized by SEM technique. The optical properties of these various morphologies of nanocrystals were also investigated, and it indicates that the SPR band shifts red while the shape of nanoparticles evolves from transitional truncated octahedral to octahedral, whose resonant bands are transferred from 590 nm to 620 nm.

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McNaughter, P. D., J. C. Bear, A. G. Mayes, I. P. Parkin et P. O'Brien. « The in situ synthesis of PbS nanocrystals from lead(II) n -octylxanthate within a 1,3-diisopropenylbenzene–bisphenol A dimethacrylate sulfur copolymer ». Royal Society Open Science 4, n^o 8 (août 2017) : 170383. http://dx.doi.org/10.1098/rsos.170383.

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The synthesis of lead sulfide nanocrystals within a solution processable sulfur ‘inverse vulcanization’ polymer thin film matrix was achieved from the in situ thermal decomposition of lead(II) n -octylxanthate, [Pb(S 2 COOct) 2 ]. The growth of nanocrystals within polymer thin films from single-source precursors offers a faster route to networks of nanocrystals within polymers when compared with ex situ routes. The ‘inverse vulcanization’ sulfur polymer described herein contains a hybrid linker system which demonstrates high solubility in organic solvents, allowing solution processing of the sulfur-based polymer, ideal for the formation of thin films. The process of nanocrystal synthesis within sulfur films was optimized by observing nanocrystal formation by X-ray photoelectron spectroscopy and X-ray diffraction. Examination of the film morphology by scanning electron microscopy showed that beyond a certain precursor concentration the nanocrystals formed were not only within the film but also on the surface suggesting a loading limit within the polymer. We envisage this material could be used as the basis of a new generation of materials where solution processed sulfur polymers act as an alternative to traditional polymers.

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Feng, Bin, Feng Teng, Ai-Wei Tang, Yan Wang, Yan-Bing Hou et Yong-Sheng Wang. « Synthesis and Optical Properties of L-Cysteine Hydrochloride-Stabilized CdSe Nanocrystals in a New Alkali System ». Journal of Nanoscience and Nanotechnology 8, n^o 3 (1 mars 2008) : 1178–82. http://dx.doi.org/10.1166/jnn.2008.18168.

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Water-soluble CdSe nanocrystals were synthesized in a new alkali system at lower temperatures by using L-cysteine hydrochloride as a stabilizer and Na2SeSO3 as a selenium source to enable the synthesis of CdSe nanocrystals in a wider range of pHvalues. The CdSe nanocrystal powder was characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. We systematically investigated the effect of synthesis conditions on the optical properties of the L-cysteine hydrochloride-stabilized CdSe nanocrystals, and found that different sizes of CdSe nanocrystals can be obtained by changing the pHvalue, the molar ratio of L-cysteine hydrochloride to Cd2+, or the refluxing time. The emission maxima of the obtained CdSe nanocrystals can be tuned in a wider range from 477 to 575 nm by changing the pHvalue from 7 to 13. We observed an obvious blue-shift of the absorption and photoluminescence peak position by varying the molar ratio of L-Cys to Cd2+ from 3.5:1 to 2:1 at the same pHvalue. The size of the obtained nanocrystals increased and the full width at half maximum became narrower as reflux time increased. Transmission electron microscopy images indicate that the as-prepared CdSe nanocrystals have a good dispersion, which means that L-cysteine hydrochloride can control the grouping of CdSe nanocrystals excellently as a stabilizer in the new alkali system.

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Yuvakkumar, R., et Sun Ig Hong. « Baddeleyite Type Monoclinic Zirconium Oxide Nanocrystals Formation ». Advanced Materials Research 1102 (mai 2015) : 79–82. http://dx.doi.org/10.4028/www.scientific.net/amr.1102.79.

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We report successful synthesis of baddeleyite type monoclinic zirconium oxide nanocrystals formation. The product mixture of zirconium incubated at room temperature for 7 days were thoroughly investigated employing X-ray diffraction, Raman spectroscopy and transmission electron microscopy studies. XRD and Raman studies revealed the formation of baddeleyite type monoclinic zirconium oxide nanocrystals. TEM studies revealed the nanocrystal formation with size ranging from 100 nm to 200 nm.

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Lin, Fang Hsin, et Reuy An Doong. « Synthesis of Ferrite Nanoparticle and Ferrite-Gold Heterostructures ». Advanced Materials Research 123-125 (août 2010) : 251–55. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.251.

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The synthesis of uniform and monodispersed magnetic and optical nanocrystals has received much attention in recent years due to the size-dependent physicochemical properties. In this study, we have demonstrated a general approach for the synthesis of size-tunable ferrite and gold nanocrystals and their nanocomposite. The monodispersed magnetite nanocrystals were obtained by thermal decomposition of iron-oleate complex in a high boiling point solvent in presence of oleylamine and oleic acid. The size of magnetite nanocrystal can be tuned from 7 – 11nm by changing the amount of iron-oleate complex. The other key parameters such as temperature, amount of capping agents, types of solvent were also discussed. This synthetic procedure could also apply to synthesis other type of ferrite nanocrystals. When Mn-acetate was partially substituted for iron-oleate in a 1:2 ratio in the same reaction conditions as in the synthesis of Fe3O4, monodispersed MnFe2O4 nanocrytals with 14nm could be obtained. Except those magnetic nanocrystals, we also synthesized various sizes of monodispersed gold nanocrystals by reducing HAuCl4 in presence of t-butylamine-borane and oleylamine. By varying the reaction temperature, the particle size could be well-tuned from 2nm to 8nm with the characteristic surface plasmon absorption between 510 and 520 nm. For Fe3O4/Au composite, it was prepared via the decomposition of iron-oleate over the surface of the Au nanoparticles. The mean size of the Fe3O4/Au nanocomposite was ∼17 nm which shows a saturation magnetization of 46.92 emu/g and absorption peak at 512nm. These composites with both magnetic and optical properties would make them very promising in the fields of biomedine and environment.

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Park, Keum Hwan, Mun Ho Kim, Sang Hyuk Im et O. Ok Park. « Electrically bistable Ag nanocrystal-embedded metal–organic framework microneedles ». RSC Advances 6, n^o 69 (2016) : 64885–89. http://dx.doi.org/10.1039/c6ra13014c.

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Electrically bistable Ag nanocrystal-embedded metal–organic frameworks (MOF) were synthesized using a one-pot synthetic method by introducing melamine into a polyol process for the synthesis of Ag nanocrystals.

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Peng, Xin Yan, et En Yong Ding. « Novel Synthesis of TiO₂ Nanocrystals Induced by Nanocrystal Cellulose ». Applied Mechanics and Materials 117-119 (octobre 2011) : 944–48. http://dx.doi.org/10.4028/www.scientific.net/amm.117-119.944.

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A new method was developed to synthesize high active TiO2 nanocrystals by the hydrolysis of titanium (IV) chloride in water at 40-80°C, employing nanocrystal cellulose (NCC) as morphology controlling agent. The obtained samples were characterized with transmission electron microscopy (TEM), X-ray diffraction (XRD), and ultraviolet-visible spectrophotometer. TEM investigations revealed that the crystals synthesized at 40-60°C were flower-like which was composed of nanoneedles, and when the temperature rose up to 70-80°C, cubic nanocrystals with an edge length of 100-200 nm were observed. XRD results showed that the crystalline phase of the nanocrystals had a strong dependence on the temperature and aging time, and the content of rutile phase increased with increasing either the temperature or the aging time. The photocatalytic activities of the samples were tested by the degradation of methyl orange in aqueous solution under high pressure mercury lamp. The experimental results revealed that cubic nanocrystals showed much higher photoactivity than flower-like ones.

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Xu, Lili, Man Wang, Qing Chen, Jiajia Yang, Wubin Zheng, Guanglei Lv, Zewei Quan et Chunxia Li. « Rare Earth Hydroxide as a Precursor for Controlled Fabrication of Uniform β-NaYF4 Nanoparticles : A Novel, Low Cost, and Facile Method ». Molecules 24, n^o 2 (19 janvier 2019) : 357. http://dx.doi.org/10.3390/molecules24020357.

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In recent years, rare earth doped upconversion nanocrystals have been widely used in different fields owing to their unique merits. Although rare earth chlorides and trifluoroacetates are commonly used precursors for the synthesis of nanocrystals, they have certain disadvantages. For example, rare earth chlorides are expensive and rare earth trifluoroacetates produce toxic gases during the reaction. To overcome these drawbacks, we use the less expensive rare earth hydroxide as a precursor to synthesize β-NaYF4 nanoparticles with multiform shapes and sizes. Small-sized nanocrystals (15 nm) can be obtained by precisely controlling the synthesis conditions. Compared with the previous methods, the current method is more facile and has lower cost. In addition, the defects of the nanocrystal surface are reduced through constructing core–shell structures, resulting in enhanced upconversion luminescence intensity.

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Li, Dehui, Weichen Qi, Jinglei Xiao, Jing Yang, Yong Wu, Qiao Gao et Shengyong Zhai. « One-Pot Synthesis of Zincblende CuInSe2 Nanocrystals via a Green Solution Reaction Route ». Nano 12, n^o 09 (septembre 2017) : 1750107. http://dx.doi.org/10.1142/s1793292017501077.

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The facile and ecofriendly method for the synthesis of a suitable colloidal nanocrystal ink plays an important role in the field of solar cells. Here, we describe our recent efforts toward this direction by a simple one-pot colloidal method to engineer CuInSe2 (CISe) nanocrystals with cubic zincblende (ZB) structure. The suitable band gap value and obvious photoresponse of the as-synthesized CISe nanocrystals indicate their potential application in the field of thin film solar cells. In addition, a possible crystal growth mechanism has been suggested for the formation of ZB CISe.

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López-Domínguez, Pedro, et Isabel Van Driessche. « Colloidal Oxide Perovskite Nanocrystals : From Synthesis to Application ». CHIMIA International Journal for Chemistry 75, n^o 5 (28 mai 2021) : 376–86. http://dx.doi.org/10.2533/chimia.2021.376.

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Nanocrystals (NCs) are complex systems that offer a superior level of detailed engineering at the atomic level. The large number of novel and revolutionary applications have made nanocrystals of special interest. In particular oxide perovskites are one of the most widely investigated family of materials in solid-state chemistry, especially for their ferroelectric and superconducting properties. In addition to these well-known properties, perovskites show good electrical conductivity (close to metals), ion conductivity and mixed ionic-electronic conductivity. In that sense, controlled synthesis of nanomaterials with special care over size and shape are essential in many fields of science and technology. Although it is well-known that physical methods deliver excellent quality nanomaterials, their high production cost has increased the interest to more affordable alternative chemical processes. In this review, we focus on the preparation of sub-10 nm oxide perovskite nanocrystals and the main strategies used to control the final properties of the obtained products. In the second part, we present the methods available for nanocrystal solutions processing together with the most remarkable applications foreseen.

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Yin, Ming, Amanda Willis, Franz Redl, Nicholas J. Turro et Stephen P. O’Brien. « Influence of Capping Groups on the Synthesis of γ-Fe2O3 Nanocrystals ». Journal of Materials Research 19, n^o 4 (avril 2004) : 1208–15. http://dx.doi.org/10.1557/jmr.2004.0157.

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Monodisperse and uniform γ-Fe2O3 (maghemite) nanocrystals of variable size were prepared by thermal decomposition of iron pentacarbonyl [Fe(CO)5] in the presence of surfactants, following controlled oxidation with trimethylamine N-oxide as a mild oxidant. The influence of carboxylic acids with variable alkyl carbon chain lengths on the synthesis of γ-Fe2O3 nanocrystals was investigated. The effect of the molar ratios of surfactant to iron precursor was also studied. The nanocrystals were characterized by x-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD showed the particles were highly crystalline at the nanometer scale. The results showed that the size and shape of the nanocrystal is strongly influenced by the decomposition temperature of iron pentacarbonyl and closely related to the length of carbon chain of the capping groups and the molar ratio of surfactant to iron precursor. Following controlled evaporation from nonpolar solvents, self-assembly into two-dimensional arrays could be observed by TEM. It was also found that the distance between the nanocrystals in self-assembled structures matched the length of the capping molecules very well.

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Kim, Byung Hyo, Junyoung Heo, Sungin Kim, Cyril F. Reboul, Hoje Chun, Dohun Kang, Hyeonhu Bae et al. « Critical differences in 3D atomic structure of individual ligand-protected nanocrystals in solution ». Science 368, n^o 6486 (2 avril 2020) : 60–67. http://dx.doi.org/10.1126/science.aax3233.

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Precise three-dimensional (3D) atomic structure determination of individual nanocrystals is a prerequisite for understanding and predicting their physical properties. Nanocrystals from the same synthesis batch display what are often presumed to be small but possibly important differences in size, lattice distortions, and defects, which can only be understood by structural characterization with high spatial 3D resolution. We solved the structures of individual colloidal platinum nanocrystals by developing atomic-resolution 3D liquid-cell electron microscopy to reveal critical intrinsic heterogeneity of ligand-protected platinum nanocrystals in solution, including structural degeneracies, lattice parameter deviations, internal defects, and strain. These differences in structure lead to substantial contributions to free energies, consequential enough that they must be considered in any discussion of fundamental nanocrystal properties or applications.

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Ding, Yong Ling, Hua Dong Sun, Kang Ning Sun et Fu Tian Liu. « Water-Based Route to Synthesis of High-Quality UV-Blue Photoluminescing ZnSe/ZnS Core/Shell Quantum Dots and their Physicochemical Characterization ». Key Engineering Materials 680 (février 2016) : 553–57. http://dx.doi.org/10.4028/www.scientific.net/kem.680.553.

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Epitaxially overgrowing a semiconductor material with higher bandgap around the QDs has proven to be a crucial approach for improving the PL efficiency and stability of nanocrystals. In this paper, a ZnS shell was deposited around ZnSe nanocrystal cores via a noninjection approach in aqueous media. The deposition procedure conducted at 100°C in a reaction flask in the presence of the shell precursor compounds, together with the crude ZnSe nanocrystal cores and the thiol ligand glutathione. The influences of various experimental variables, including the reaction time, amount of thiourea, as well as pH value, on the growth rate and luminescent properties of the obtained core/shell nanocrystals have been systematically investigated. In comparison with the original ZnSe nanocrystals, the PL efficiency of the obtained ZnSe/ZnS core/shell nanostructures can be improved significantly with a QY up to 62.8%.

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Hu, Long, Robert J. Patterson, Zhilong Zhang, Yicong Hu, Dengbing Li, Zihan Chen, Lin Yuan et al. « Enhanced optoelectronic performance in AgBiS2 nanocrystals obtained via an improved amine-based synthesis route ». Journal of Materials Chemistry C 6, n^o 4 (2018) : 731–37. http://dx.doi.org/10.1039/c7tc05366e.

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Liu, Xuewen, et Eun-Cheol Lee. « Advancements in Perovskite Nanocrystal Stability Enhancement : A Comprehensive Review ». Nanomaterials 13, n^o 11 (23 mai 2023) : 1707. http://dx.doi.org/10.3390/nano13111707.

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Over the past decade, perovskite technology has been increasingly applied in solar cells, nanocrystals, and light-emitting diodes (LEDs). Perovskite nanocrystals (PNCs) have attracted significant interest in the field of optoelectronics owing to their exceptional optoelectronic properties. Compared with other common nanocrystal materials, perovskite nanomaterials have many advantages, such as high absorption coefficients and tunable bandgaps. Owing to their rapid development in efficiency and huge potential, perovskite materials are considered the future of photovoltaics. Among different types of PNCs, CsPbBr3 perovskites exhibit several advantages. CsPbBr3 nanocrystals offer a combination of enhanced stability, high photoluminescence quantum yield, narrow emission bandwidth, tunable bandgap, and ease of synthesis, which distinguish them from other PNCs, and make them suitable for various applications in optoelectronics and photonics. However, PNCs also have some shortcomings: they are highly susceptible to degradation caused by environmental factors, such as moisture, oxygen, and light, which limits their long-term performance and hinders their practical applications. Recently, researchers have focused on improving the stability of PNCs, starting with the synthesis of nanocrystals and optimizing (i) the external encapsulation of crystals, (ii) ligands used for the separation and purification of nanocrystals, and (iii) initial synthesis methods or material doping. In this review, we discuss in detail the factors leading to instability in PNCs, introduce stability enhancement methods for mainly inorganic PNCs mentioned above, and provide a summary of these approaches.

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Gerdes, Frauke, Eugen Klein, Sascha Kull, Mohammad Mehdi Ramin Moayed, Rostyslav Lesyuk et Christian Klinke. « Halogens in the Synthesis of Colloidal Semiconductor Nanocrystals ». Zeitschrift für Physikalische Chemie 232, n^o 9-11 (28 août 2018) : 1267–80. http://dx.doi.org/10.1515/zpch-2018-1164.

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Abstract In this review, we highlight the role of halogenated compounds in the colloidal synthesis of nanostructured semiconductors. Halogen-containing metallic salts used as precursors and halogenated hydrocarbons used as ligands allow stabilizing different shapes and crystal phases, and enable the formation of colloidal systems with different dimensionality. We summarize recent reports on the tremendous influence of these compounds on the physical properties of nanocrystals, like field-effect mobility and solar cell performance and outline main analytical methods for the nanocrystal surface control.

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Li, Xinke, Fangtian You, Hongshang Peng et Shihua Huang. « Synthesis and Near-Infrared Luminescent Properties of NaGdF4:Nd3+@NaGdF4 Core/Shell Nanocrystals with Different Shell Thickness ». Journal of Nanoscience and Nanotechnology 16, n^o 4 (1 avril 2016) : 3940–44. http://dx.doi.org/10.1166/jnn.2016.11818.

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The near-infrared to near-infrared (NIR-to-NIR) photoluminescence of nanocrystals has outstanding advantages in biological imaging. NaGdF4:Nd3+ core nanocrystals and NaGdF4:Nd3+@NaGdF4 core/shell nanocrystals with different shell thicknesses were synthesized by a simple solvothermal method. The obtained nanocrystals were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The phase of all nanocrystals is hexagonal. NaGdF4:Nd3+ core nanocrystals have an average size of 6 nm. By controlling core–shell ratio for 1:2 and 1:3, we obtained NaGdF4:Nd3+@NaGdF4 core/shell nanocrystals with average sizes of 10 nm and 11 nm, respectively. When excited at 808 nm, strong NIR emission was observed. The emission peaks at ∼860 nm, ∼1060 nm and ∼1330 nm correspond to the transitions from the 4F3/2 statetothe 4I9/2, 4I11/2 and 4I13/2 state of Nd3+ ions, respectively. The emission intensity of NaGdF4:Nd3+@NaGdF4 core/shell nanocrystals is stronger than that of the core. The intensity increases with the increase of shell thickness. The shell improves the luminous efficiency by reducing surface defects. The decay time of Nd3+ emission in NaGdF4:Nd3+@NaGdF4 core/shell nanocrystal is longer than that in NaGdF4:Nd3+ core, indicating that the shell isolates effectively the emitting ions (Nd3+)from the quenching defects. With the increase of shell thickness, the decay time becomes longer. Within a certain range of shell thickness, thicker shell can protect the emitting Nd3+ ions on the surface of core nanocrystals more effectively.

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Clarysse, Jasper, Annina Moser, Olesya Yarema, Vanessa Wood et Maksym Yarema. « Size- and composition-controlled intermetallic nanocrystals via amalgamation seeded growth ». Science Advances 7, n^o 31 (juillet 2021) : eabg1934. http://dx.doi.org/10.1126/sciadv.abg1934.

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Intermetallic nanocrystals are a large family of emerging materials with extensive applications in many fields. Yet, a generalized synthetic method for intermetallic nanocrystals is lacking. Here, we report the development of a colloidal synthesis method based on amalgamation of monometallic nanocrystal seeds with low–melting point metals. We use this approach to achieve crystalline and compositionally uniform intermetallic nanocrystals of Au-Ga, Ag-Ga, Cu-Ga, Ni-Ga, Pd-Ga, Pd-In, and Pd-Zn compounds. We demonstrate both compositional tunability across the phase spaces (e.g., AuGa2, AuGa, Au7Ga2, and Ga-doped Au), size tunability (e.g., 14.0-, 7.6-, and 3.8-nm AuGa2), and size uniformity (e.g., 5.4% size deviations). This approach makes it possible to systematically achieve size- and composition-controlled intermetallic nanocrystals, opening up a multitude of possibilities for these materials.

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Shi, He-Ping, Da-Wei Lin et Rui-feng Wu. « Synthesis of High-Quality Carboxyl End-Functionalized Poly(3-hexylthiophene)/CdSe Nanocomposites ». Journal of Nanomaterials 2019 (15 septembre 2019) : 1–8. http://dx.doi.org/10.1155/2019/1251598.

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Carboxyl end-functionalized poly(3-hexylthiophene) (P3HT-COOH) was grafted chemically with CdSe nanocrystals (NCs) by a phosphine-free method. The particle quality of P3HT-COOH/CdSe nanocomposites was better than that of P3HT/CdSe nanocomposites, which were synthesized using the same method. Nanocrystals with controllable particle size exhibited a wurtzite crystalline structure and showed excellent nanocrystal dispersion in the P3HT-COOH matrix. Photoluminescence (PL) characterization performed on nanocomposites suggested the efficient charge transfer at the P3HT-COOH/CdSe interface. This approach based on the phosphine-free method is not only environmentally friendly but also highly efficient.

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Murphy, Catherine J., Tapan K. Sau, Anand Gole et Christopher J. Orendorff. « Surfactant-Directed Synthesis and Optical Properties of One-Dimensional Plasmonic Metallic Nanostructures ». MRS Bulletin 30, n^o 5 (mai 2005) : 349–55. http://dx.doi.org/10.1557/mrs2005.97.

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AbstractOne-dimensional metallic nanostructures such as nanorods and nanowires are of tremendous interest for electronic, sensing, and catalytic applications. Shape anisotropy introduces new optical properties in gold and silver nanoparticles, such as longitudinal plasmon resonance bands in the visible and near-IR portion of the spectrum. Different approaches employed for the shape-controlled synthesis of silver and gold nanocrystals include chemical, electrochemical, and physical methods. The chemical route for the synthesis of nanorods and nanowires, in which metal salts are reduced in an aqueous solution, is one of the most widely used methods. This route commonly employs a surfactant as the directing agent to introduce asymmetry in the nanocrystal shape. Variation in the concentration of precursor salt and the surfactant, the nature of the surfactant, the nature and concentration of reducing agents, the presence of external salts, and the pH of the reaction solution all affect nanocrystal shape, dimension, and yield. The size and shape of the nanocrystals affect the position of the plasmon bands, which in turn has been widely used in surface-enhanced spectroscopies that include both Raman and fluorescence. The aqueous, surfactant-directed route also promises the synthesis of more complex nanostructures with additional desirable properties.

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Gu, X. Wendy, Xingchen Ye, David M. Koshy, Shraddha Vachhani, Peter Hosemann et A. Paul Alivisatos. « Tolerance to structural disorder and tunable mechanical behavior in self-assembled superlattices of polymer-grafted nanocrystals ». Proceedings of the National Academy of Sciences 114, n^o 11 (27 février 2017) : 2836–41. http://dx.doi.org/10.1073/pnas.1618508114.

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Large, freestanding membranes with remarkably high elastic modulus (>10 GPa) have been fabricated through the self-assembly of ligand-stabilized inorganic nanocrystals, even though these nanocrystals are connected only by soft organic ligands (e.g., dodecanethiol or DNA) that are not cross-linked or entangled. Recent developments in the synthesis of polymer-grafted nanocrystals have greatly expanded the library of accessible superlattice architectures, which allows superlattice mechanical behavior to be linked to specific structural features. Here, colloidal self-assembly is used to organize polystyrene-grafted Au nanocrystals at a fluid interface to form ordered solids with sub-10-nm periodic features. Thin-film buckling and nanoindentation are used to evaluate the mechanical behavior of polymer-grafted nanocrystal superlattices while exploring the role of polymer structural conformation, nanocrystal packing, and superlattice dimensions. Superlattices containing 3–20 vol % Au are found to have an elastic modulus of ∼6–19 GPa, and hardness of ∼120–170 MPa. We find that rapidly self-assembled superlattices have the highest elastic modulus, despite containing significant structural defects. Polymer extension, interdigitation, and grafting density are determined to be critical parameters that govern superlattice elastic and plastic deformation.

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Rangel-Chávez, L. G., M. I. Neria-González, A. Márquez-Herrera, M. Zapata-Torres, E. Campos-González, O. Zelaya-Angel, A. Guillen-Cervantes, J. L. Fernandez-Muñoz et M. Melendez-Lira. « Synthesis of CdS Nanocrystals by Employing the By-Products of the Anaerobic Respiratory Process ofDesulfovibrio alaskensis6SR Bacteria ». Journal of Nanomaterials 2015 (2015) : 1–7. http://dx.doi.org/10.1155/2015/260397.

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A novel methodology for the direct synthesis of CdS nanoparticles, using a biological agent that avoids the extracellular processing, and the results of the characterization of CdS nanocrystals are presented. The by-products of the anaerobic respiratory process ofDesulfovibrio alaskensis6SR along with aqueous solutions of Cd salts were successfully employed to produce CdS nanocrystals with mixed cubic and hexagonal phases. Nanocrystal size has a narrow size distribution with little dependence on the Cd concentration. Both the presence of the crystallographic cubic phase and the crystalline order decrease as Cd concentration increases. The band gap values obtained from optical transmission measurements are lower than those of the bulk crystal. Raman spectroscopy characterization agrees with electron transmission microscopy images and X-ray diffraction results indicating that the method promotes the formation of high structural quality nanocrystals when low concentrations of the Cd salt are used.

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Perner, Verena, Thomas Rath, Franz Pirolt, Otto Glatter, Karin Wewerka, Ilse Letofsky-Papst, Peter Zach, Mathias Hobisch, Birgit Kunert et Gregor Trimmel. « Hot injection synthesis of CuInS2 nanocrystals using metal xanthates and their application in hybrid solar cells ». New Journal of Chemistry 43, n^o 1 (2019) : 356–63. http://dx.doi.org/10.1039/c8nj04823a.

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Copper indium sulfide nanocrystals with sizes of 3–4 nm were synthesized from metal xanthates in a hot injection reaction. After ligand exchange, their performance as acceptors in polymer/nanocrystal hybrid solar cells was evaluated.

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ARSHI, NISHAT, FAHEEM AHMED, M. S. ANWAR, SHALENDRA KUMAR, BON HEUN KOO, JUNQING LU et CHAN GYU LEE. « NOVEL AND COST-EFFECTIVE SYNTHESIS OF SILVER NANOCRYSTALS : A GREEN SYNTHESIS ». Nano 06, n^o 04 (août 2011) : 295–300. http://dx.doi.org/10.1142/s1793292011002743.

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This paper reports the study on the synthesis and characterization of silver nanocrystals by a two-step synthesis procedure. The first step is the solution-free hand grinding of silver foil and sugar at room temperature for few minutes. The second step is the thermal decomposition of silver/sugar composite to form silver nanocrystals. The as-synthesized silver nanocrystals were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet visible (UV/Vis) spectroscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM) studies. The XRD pattern showed a face-centered cubic structure (single phase) with high crystallinity. The lattice parameters calculated from XRD pattern were found to be a = 4.12 Å for silver nanocrystals with average grain size of ~ 19 nm. The energy dispersive analysis of X-rays (EDAX) of silver nanocrystals confirmed the presence of silver and no peak of any secondary phase was detected. FESEM and AFM studies showed that the crystals have cube-like morphology. TEM results showed that the size of silver nanocrystals was found to be ~ 22 nm. This novel synthesis route, not reported earlier, would be a promising candidate for a variety of future applications of silver nanocrystals.

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Farmonovich, Ishankulov Alisher. « Synthesis and Optical-dimensional Properties of Hybrid CDSE/ZNS Nanocrystals ». Journal of Advanced Research in Dynamical and Control Systems 12, SP7 (25 juillet 2020) : 2201–5. http://dx.doi.org/10.5373/jardcs/v12sp7/20202344.

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Sun, Dong-Mei, Da-Zhang Zhu et Qing-Sheng Wu. « Bi-template effect of a vegetal system on the synthesis of alkaline-earth tungstate nanocrystals ». Journal of Materials Research 24, n^o 2 (février 2009) : 347–51. http://dx.doi.org/10.1557/jmr.2009.0072.

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The MBS (mung bean sprouts) vegetal system, with its high penetrability, high selectivity, and space restriction, was explored to control nanocrystal synthesis. We found that the inside and outside of MBS have different structures and ion transformation properties. Two nanocrystals with distinct morphology, the nanorod and the nanosphere, were grown on the outer surface and the inner stem wall of MBS, respectively. The two XWO4 (X = Ca,Sr,Ba) nanocrystals were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), and Fourier transform infrared (FTIR). The FTIR spectra of nanoproducts were different from bulk products due to the nano-size effect. A presumable mechanism was also determined. This work benefits the application of nanotungstates.

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Shan, Wei Jun, Qiang Yan, Du Li, Da Wei Fang et Shu Liang Zang. « Ultrasonic Synthesis of Ag₂Se Nanocrystal in Perrhenate Solution ». Advanced Materials Research 919-921 (avril 2014) : 2109–11. http://dx.doi.org/10.4028/www.scientific.net/amr.919-921.2109.

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Ag2Se nanocrystal was successfully prepared by ultrasonic synthesis in water and ethanol systems at an ambient pressure. The powder of selenium was used as the selenium ion source. The size of the nanocrystals is in the scope of 10-20nm. The products were characterized by some means including X-ray Powder Diffraction (XRD) and Transmission Electron Microscopy (TEM) which was used to study the thermostability of the product. The result of the experiments indicated that the concentration of the reactant, the pH of the solution, the react temperature and the surfactant had some important influence on the formation and the size of the Ag2Se nanoparticles. The method we reported here is proved to be a new and an easy way to prepare the nanocrystals of metal chalcogenide.

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Kim, Young Mi, Seok Ju Lee et Ik Jin Kim. « Synthesis and Characterization of TMA-A Zeolite Nanocrystals ». Solid State Phenomena 124-126 (juin 2007) : 563–66. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.563.

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Well-controlled cubic nanocrystal of TMA-A zeolite with a size of 60~100 nm were synthesized by a hydrothermal method in a solution having a Al(i-pro)3 : 2.2 TEOS : 2.4 TMAOH: 0.3 NaOH : 200H2O composition. The single TMA-A nanocrystals has an average lattice constant of 24.61 Å having a surface area of 742.36 m2/g. Thermal treatment of TMA zeolite crystals results in the formation of an amorphous above 900oC. Environmental scanning electron microscopy (ESEM). high resolution transmission electron microscopy(HRTEM), X-ray powder diffraction(XRD), fourier transform infrared(FT-IR) spectroscopy, DTA/TGA and BET analysis were used to characterize the initial materials and the obtained products after various heat treatments.

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Sharma, Sumit Kumar, Swati Mamgain, Burhanuddin Attarwala et Aswani Yella. « ZnX2 mediated post-synthetic transformation of zero dimensional Cs4PbBr6 nanocrystals for opto-electronic applications ». Nanoscale Advances 1, n^o 7 (2019) : 2502–9. http://dx.doi.org/10.1039/c9na00244h.

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Herein we demonstrate a facile approach for the synthesis of all inorganic cesium lead halide perovskite nanocrystal composites CsPbX₃ (X = Cl, Br, I) with high quantum yield by post-synthetic modulation of zero dimensional Cs₄PbBr₆ nanocrystals with ZnX₂ salts.

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Kennedy, M. T., B. A. Korgel, J. A. Zasadzinski et H. G. Monbouquette. « Size-Controlled Synthesis of Cds Nanocrystals in Vesicles Confirmed in Situby Cryo-Transmission Electron Microscopy ». Microscopy and Microanalysis 3, S2 (août 1997) : 435–36. http://dx.doi.org/10.1017/s1431927600009065.

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Size-quantized CdS nanocrystals, synthesized within phosphatidylcholine (PC) vesicles by reaction compartmentalization, were observed in situ to confirm the proposed method of formation and to investigate the concept of membrane-mediated crystal growth. Vesicle solutions representing three different CdS nanocrystal sizes, and a solution containing unreacted CdCl2 inside vesicles, were analyzed using cryo-transmission electron microscopy (cryo-TEM). Cryo-TEM has proved capable of resolving both the vesicle bilayer and the encapsulated nanocrystal, and yields previously unknown positional information for the crystal in relation to the bilayer.Egg-PC vesicles containing Cd2+ were formed by detergent depletion, yielding vesicles of uniform size and a defined internal Cd2+ concentration. External Cd2+ was removed from the solution by cation exchange. Ammonium sulfide was added to the vesicle dispersion to produce nanocrystals via diffusion of S2- across the vesicle membrane. Particle size was predicted based upon the vesicle size, as determined from light scattering, and the encapsulated Cd2+ concentration.

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Jeong, Kwanyong, Soo Min Kim et In Su Lee. « A seed-engineering approach toward a hollow nanoreactor suitable for the confined synthesis of less-noble Ni-based nanocrystals ». Chemical Communications 51, n^o 3 (2015) : 499–502. http://dx.doi.org/10.1039/c4cc07306a.

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A hollow nanoreactor suitable for the cultivation of Ni-nanocrystals was developed through a distinct seed-engineering strategy, which involved the assembly of a catalytically active Au/Pd-heterojunction-nanocrystal inside the hollow silica nanoshell.

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Bai, Liuyang, Yuge Ouyang, Jun Song, Zhi Xu, Wenfu Liu, Jingyu Hu, Yinling Wang et Fangli Yuan. « Synthesis of Metallic Nanocrystals : From Noble Metals to Base Metals ». Materials 12, n^o 9 (8 mai 2019) : 1497. http://dx.doi.org/10.3390/ma12091497.

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Metallic nanocrystals exhibit superior properties to their bulk counterparts because of the reduced sizes, diverse morphologies, and controllable exposed crystal facets. Therefore, the fabrication of metal nanocrystals and the adjustment of their properties for different applications have attracted wide attention. One of the typical examples is the fabrication of nanocrystals encased with high-index facets, and research on their magnified catalytic activities and selections. Great accomplishment has been achieved within the field of noble metals such as Pd, Pt, Ag, and Au. However, it remains challenging in the fabrication of base metal nanocrystals such as Ni, Cu, and Co with various structures, shapes, and sizes. In this paper, the synthesis of metal nanocrystals is reviewed. An introduction is briefly given to the metal nanocrystals and the importance of synthesis, and then commonly used synthesis methods for metallic nanocrystals are summarized, followed by specific examples of metal nanocrystals including noble metals, alloys, and base metals. The synthesis of base metal nanocrystals is far from satisfactory compared to the tremendous success achieved in noble metals. Afterwards, we present a discussion on specific synthesis methods suitable for base metals, including seed-mediated growth, ligand control, oriented attachment, chemical etching, and Oswald ripening, based on the comprehensive consideration of thermodynamics, kinetics, and physical restrictions. At the end, conclusions are drawn through the prospect of the future development direction.

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Lee, Soo Jin, Woon Jo Cho, Chong Shik Chin et Il Ki Han. « Sonochemical Synthesis of Silicon Nanocrystals ». Key Engineering Materials 277-279 (janvier 2005) : 995–99. http://dx.doi.org/10.4028/www.scientific.net/kem.277-279.995.

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Silicon nanocrystals in a range from 2 nm to 5 nm were prepared from Zintl salt, soldium silicide (NaSi) by sonochemical method. This synthesis permits that the reaction be completed in only a few hours and the easy alkyl-modification of nanocrystals surface at room temperature and ambient pressure. The average size of nanocrystals measured by the dynamic light scattering analysis was 2.7 nm. The high-resolution transmission electron micrograph confirmed the material identity of nanocrystals as crystalline silicon. FT-IR spectra are consistent with the surface states of nanocrystals that are chlorine-or butyl-capped. The emission peak center moved to a longer wavelength (up to 430 nm) with the reaction time, under a 325 nm excitation.

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Yu, Jinlong, Frederik Søndergaard-Pedersen, Aref Mamakhel, Paolo Lamagni et Bo Brummerstedt Iversen. « Three-dimensional morphology of anatase nanocrystals obtained from supercritical flow synthesis with industrial grade TiOSO4 precursor ». Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 75, n^o 6 (14 novembre 2019) : 1086–95. http://dx.doi.org/10.1107/s2052520619012733.

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Anatase TiO2 (a-TiO2) nanocrystals are vital in catalytic applications both as catalysts (e.g. photodegradation) and as a carrier material (e.g. NOx removal from exhaust). The synthesis of a-TiO2 nanocrystals and their properties have been heavily scrutinized, but there exists a clear gap between the scientific literature, and the scale and price expectation of industrial application. Here it is demonstrated that the industrially most attractive Ti precursor, titanyl sulfate (TiOSO4), can be combined with the green, scalable and fast supercritical flow method to produce phase pure and highly crystalline a-TiO2 nanoparticles with high specific surface area. Control of the nanocrystal morphology is important since it is known that certain facets substantially promote catalytic activity. It is, however, in itself challenging to determine nanocrystal morphology to provide a rational basis for the synthesis control. Here we advocate the use of advanced Rietveld refinement of powder X-ray diffraction data including anisotropic size broadening models in aiding to establish the sample three-dimensional morphology. This relatively quick and robust method assists in overcoming the often encountered ambiguity inherent in two-dimensional to three-dimensional reconstruction of selected particle morphologies with transmission electron microscopy and tomography techniques.

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